Epidermal Tissue System MCQ - Practice Questions with Answers

Epidermal Tissue System

• It is the outermost tissue system of the plant body involved in protection.
• It originates from the protoderm of apical meristem.
• It consists of the tissues discussed below:

Epidermis

• It is the outermost continuous layer of parenchymatous cells in the primary plant body.
• If the epidermis is a single layer, it is called uniseriate.
• If the epidermis is multi layered, it is called multiseriate.
• Multiseriate epidermis is seen in xerophytic plants, like, Ficus, Nerium, Peperomia, Cactus.
• The cells of epidermis lack intercellular spaces. 
• In aerial parts of the plant, the outer cell wall of the epidermal cells is covered with a waxy substance called cutin.
• The layer of cutin is called cuticle.
• Cuticle never occurs in the epidermis of roots. The epidermis of root is called epiblema.
• Cuticle is also absent in submerged hydrophytes. 
• Epidermis is the protective layer that protects the underlying tissues against mechanical injury, light intensity, thermal changes, microbial attacks, general abrasion, etc.
• Epidermis stores mucilage in succulent plants.
• In some plants, it performs photosynthesis.
   

Epidermal Tissue System - Special Epidermal Structures

Lithocysts:

• Lithocysts are the epidermal cells that contain the mass of calcium carbonate called cystolith. 
• These are seen in the members of Acanthaceae, Urticaceae, Cannabaceae, and in the Indian Rubber Plant (Ficus elastica) of the family Moraceae.

Myrosin Cells:

• These are the idioblasts that store the myrosinase enzyme in the form of granules. 
• The myrosinase enzyme hydrolyses the glucosinolates.
• This acts as a deterrent to the herbivores in Brassicales.

Bulliform Cells:

• These are enlarged bubble-shaped epidermal cells.
• These are present on the adaxial surface of leaves in many monocots. (adaxial surface - upper surface; abaxial surface - lower surface).
• These are seen near the midrib.
• These help in rolling the leaves to prevent transpiration during water stress.
• These are also called motor cells.

Root hairs:

• These are the unicellular extension of the epidermal cells of roots.
• These increase the surface area of absorption.
• They collect water and mineral nutrients present in the soil and pass them on to the conducting tissues of the root.

Trichomes:

• These are the epidermal outgrowth seen in the shoot system.
• Unlike root hairs, these can be multicellular.
• These can be stellate hair, glandular hair, stinging hair, etc.
• The trichomes serve for checking excess loss of water and for protection.

Stomata:

• These are the tiny openings or pores in the epidermal system of plants, especially leaves.
• Stomata can also occur in the stem. 
• The stomata are surrounded by specialized epidermal cells called guard cells that regulate the opening and closing of stomata.
• Guard cells are generally bean-shaped in dicots and dumbbell-shaped in monocots.
• Stomata regulate the gaseous exchange and transpiration. 
• Some surrounding epidermal cells become specialized to form the subsidiary cells. 
• The stomatal aperture, guard cells, and subsidiary cells are called the stomatal aperture.